"Even the current epidemiological data, they note, do not consistently show that those who are thinnest live longest. After analyzing decades of national mortality statistics, federal researchers reported last year that exceptional thinness, a logical consequence of calorie restriction, was associated with an increased risk of death."

I would like to the point that the thinnest might have no muscles, low basal metabolic rate, no exercise. So - why should they live longer? Low calories? - What is low?

I think that low body fat should be the goal - sometimes calories are necessary to keep your muscles well and alive. "On weekends, he occasionally fasts" - which will make him loose muscle mass, as he has no body fat. Even if he had, muscle energy gets lost first.

Calorie restriction alone will not do it. You have to know when and where.